Sarcolemmal Ca2+-ATPase ability to transport Ca2+ gradually diminishes after myocardial infarction in the rat.
OBJECTIVE
Plasmalemmal Ca(2+)-ATPase (PMCA) is involved in Ca(2+) handling and the regulation of intracellular signalling pathways in the heart. However, there is no information on its functioning in heart hypertrophy and failure. We aimed to investigate the Ca(2+)-transporting ability of PMCA, Na(+)/Ca(2+) exchanger (NCX), and sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA2a), as well as the amplitude of Ca(2+) transients and cell shortening in myocytes isolated from rat hearts at various time intervals after myocardial infarction (MI).


RESULTS
The rate of Ca(2+) transport by PMCA, NCX, and SERCA2a was estimated from the rate constants of decay of electrically and caffeine-evoked Ca(2+) transients in left ventricular myocytes isolated 1 week, 1 month, and 3 months after MI. One week, 1 month, and 3 months after MI, the transporting function of PMCA decreased by 27, 41, and 67%, respectively, compared with that in time-matched sham animals. This was accompanied by increased amplitude of Ca(2+) transients, cell shortening, and SR Ca(2+) content. Carboxyeosin, a blocker of PMCA, increased the amplitude of shortening in cells extracted from control hearts. This effect was absent 1 and 3 months after MI. PMCA1, 2, and 4 mRNAs were unchanged in the ventricular muscle 3 months after MI when compared with time-matched sham animals. The transporting function of NCX was increased by 65% only 3 months after MI, whereas that of SERCA2a was decreased by approximately 18% at all three time points after MI.


CONCLUSIONS
The ability of PMCA to transport Ca(2+) progressively decreases over 3 months after MI. This decrease may contribute to the increase in amplitude of Ca(2+) transients and myocyte shortening.
Mackiewicz
Urszula
U
Department of Clinical Physiology, Postgraduate Medical School, Marymoncka Str 99/101, 01-813 Warsaw, Poland. urszulam@cmkp.edu.pl
Maczewski
Michał
M
Konior
Anna
A
Tellez
James O
JO
Nowis
Dominika
D
Dobrzynski
Halina
H
Boyett
Mark R
MR
Lewartowski
Bohdan
B
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D004195:Disease Models, Animal; D015536:Down-Regulation; D004558:Electric Stimulation; D008297:Male; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000201:enzymology* / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology*; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D013997:Time Factors; D020257:Ventricular Remodeling
C506948:Atp2a2 protein, rat; C506961:Atp2b2 protein, rat; D012333:RNA, Messenger; D019831:Sodium-Calcium Exchanger; D002110:Caffeine; D053499:Plasma Membrane Calcium-Transporting ATPases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506955:Atp2b1 protein, rat; D002118:Calcium